In heavy nonstick pan, melt 2 tbsp butter until foamy on medium high heat.
Add onion to pan and cook, stirring occasionally, until soft - about 4 minutes.
Add garlic and shallot and cook until fragrant, about 1 minute.
Add asparagus and cherry tomatoes to pan.
Cook another 4 minutes, until tomatoes cook down and asparagus is bright green.
Add in shrimp and lemon slices, toss.
Generously season with salt, pepper, herbs.
Add additional 2 tbsp butter.
Continue cooking until shrimp is pink and white (no longer translucent and grey), about 5 minutes.
Do not overcook shrimp - when shrimp is done, remove from heat and serve.
Remove lemon slices when serving.